Benzene-azo-nitro-ethane.
Those not containing a nitro group may be prepared by the oxidation of the corresponding mixed hydrazo compounds with mercuric oxide. E. Bamberger (Ber., 1898, 31, p. 455) has shown that the nitro-alkyl derivatives behave as though they possess the constitution of hydrazones, for on heating with dilute alkalies they split more or less readily into an alkaline nitrite and an acid hydrazide:
C6H5NH·N:C(NO2)CH3 + NaOH = NaNO2 + C6H5NH·NH·CO·CH3.
Benzene-azo-methane, C6H5·N2·CH3, is a yellow oil which boils at 150° C. and is readily volatile in steam. Benzene-azo-ethane, C6H5·N2·C2H5, is a yellow oil which boils at about 180° C. with more or less decomposition. On standing with 60% sulphuric acid for some time, it is converted into the isomeric acetaldehyde-phenylhydrazone, C6H5NH·N:CH·CH3 (Ber., 1896, 29, p. 794).
The diazo cyanides, C6H5N2·CN, and carboxylic acids, C6H5·N2·COOH, may also be considered as mixed azo derivatives. Diazobenzenecyanide, C6H5N2·CN, is an unstable oil, formed when potassium cyanide is added to a solution of a diazonium salt. Phenyl-azo-carboxylic acid, C6H5·N2·COOH, is obtained in the form of its potassium salt when phenylsemicarbazide is oxidized with potassium permanganate in alkaline solution (J. Thiele, Ber., 1895, 28, p. 2600). It crystallizes in orange-red needles and is decomposed by water. The corresponding amide, phenyl-azo-carbonamide, C6H5N2·CONH2, also results from the oxidation of phenylsemicarbazide (Thiele, loc. cit.), and forms reddish-yellow needles which melt at 114° C. When heated with benzaldehyde to 120° C. it yields diphenyloxytriazole, (C6H5)2CN3C(OH).
AZOIMIDE, or Hydrazoic Acid, N3H, a compound of nitrogen and hydrogen, first isolated in 1890 by Th. Curtius (Berichte, 1890, 23, p. 3023). It is the hydrogen compound corresponding to P. Greiss' diazoimino benzene, C6H5N3, which is prepared by the addition of ammonia to diazobenzene perbromide.
Curtius found that benzoyl glycollic acid gave benzoyl hydrazine with hydrazine hydrate:
C6H5OCO·CH2COOH + 2N2H4·H2O = H2O + C6H5CONH·NH2 + NH2·NH·CH2·COOH.
(Ethyl benzoate may be employed instead of benzoyl glycollic acid for this reaction.) This compound gave a nitroso compound with nitrous acid, which changed spontaneously into benzoylazoimide by loss of water: